The present invention relates to a clutch cover assembly, particularly to a clutch cover assembly with a mechanism for keeping a set load constant regardless of wear of the friction members.
The clutch cover assembly is, generally, fixed to a flywheel of the engine and presses Friction members of tile clutch disc against the flywheel in order to transmit tile power of the engine to the speed change gear mechanism. In this kind of the clutch cover assembly and the clutch disc, tile wear of the friction members shortens their lives. It is possible to lengthen the life of the clutch disc by increasing effective thickness of facings. For example, the facings are attached to the cushioning plate without using rivets.
When the facings are worn, the posture of the diaphragm spring changes, whereby the set load of the diaphragm spring against the pressure plate decreases. A clutch cover assembly disclosed in Japanese Patent Laying-Open No. 27092/1988 makes the set load of the diaphragm spring return to the initial load automatically in the course of racing wear.
This clutch cover assembly has, as shown in FIG. 17, a pressure plate 1 formed with an annular groove 2 in which a diaphragm spring posture maintenance mechanism 3 is arranged. The mechanism 3 comprises an outer fulcrum ring 5 and an inner fulcrum ring against which outer periphery of the diaphragm spring 4 presses, slide keys 7 and 8 located between the fulcrum rings 5 and 6, and the bottom of the groove 2, respectively. Each of slide keys 7 and 8 is formed with an inclined surface which decreases in axial height proceeding radially outward. The fulcrum rings 5 and 6 are formed with inclined surfaces corresponding to the inclined surfaces of the slide keys 7 and 8. The slide keys 7 and 8 are urged radially outward by respective springs 9 and 10.
As facings 11 of the clutch disc wear, the inner fulcrum ring 6 is moved toward the diaphragm spring 4 by the springs 10 and the slide keys 8 according to the wear amount. At the release operation, the outer fulcrum ring 5 moves according to the amount by which the inner fulcrum ring 6 moved. Consequently, the posture of the diaphragm spring 4 is maintained so that the set load of the diaphragm spring 4 automatically returns to the initial value.
In the above-mentioned structure, when the engine rotation speed rises centrifugal force is applied to the slide keys 7 and 8, which makes the slide keys move radially outward. In this case, even though the facings 11 are not worn, the slide keys 7 and 8 move so as to move the fulcrum rings 5 and 6 axially. As a result, it is impossible to make the wear amount of the facings 11 correspond to the moving amount of the fulcrum rings 5 and 6 correctly and to maintain the initial set load of the diaphragm spring 4.